During the first two years of its tour of the Saturn system, Cassini has been flying-by some of the most interesting icy satellites. Gravity field results obtained from the orbital fit of radiometric data acquired during these close encounters with Phoebe, Iapetus, Enceladus, Hyperion, Dione and Rhea are presented. These results were then used to infer information about the internal structure of these bodies. This paper describes the technique used for the short-arc orbit determination process, the data calibration and analysis procedure, and the mass and gravity field results, emphasizing the advantages offered by Cassini’s advanced deep-space tracking system.